Polyethylene terephthalate has recently been used as a support for a magnetic recording medium. Polyethylene terephthalate is stretched and highly crystallized and, therefore, has excellent properties in both resistance against organic solvents and mechanical strength.
A magnetic layer which is obtained by dispersing a ferromagnetic particle in a binder to prepare a coating composition and coating it on a support has an extremely low mechanical strength. Accordingly, a magnetic layer which is prepared without providing a subbing layer on a support can be readily destroyed by the application of a slight force. It is extremely difficult to obtain a magnetic layer which adheres strongly to a support. The simplest and most useful resolution to this problem is to provide a magnetic layer with a snubbing layer.
The composition of a subbing layer is disclosed in U.S. Pat. No. 3,730,767, Japanese Patent Publication No. 10243/74, and Japanese Patent Application (OPI) Nos. 46406/74, 46407/74, 32905/75, 32906/75 and 32907/75 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"). However, these compositions do not always provide satisfactory results.